Polymerase-immobilized electrode

The present invention is to reduce a false signal in an apparatus for electrochemically decoding a base sequence of DNA, which false signal is caused by a phenomenon that even unreacted nucleotide 5′-triphosphate derivatives remaining in the solution are electrochemically converted on an electrode. The present invention provides a polymerase-immobilized electrode that comprises an electroconductive substrate and a polymerase unit immobilized on the surface of the electroconductive substrate, wherein the polymerase unit comprises a polymerase part, an anchor part and an electroconductive part, which are linked in an order of the polymerase part, the anchor part and the electroconductive part, or in an order of the polymerase part, the electroconductive part and the anchor part; and the polymerase unit is immobilized on the electroconductive substrate by the anchor part; wherein a free end of the electroconductive part, not immobilized on the electroconductive substrate, is located in the vicinity of an active site of the polymerase part.